Note that the points discussed below are not necessarily admitted to be prior art.
Hydroisomerization of hydrocarbons is an important technology in the refining of oil. The branched isomers produced by the hydroisomerization reaction can significantly reduce the pour point of lubricating oil, increase the viscosity-temperature characteristics of diesel and increase the octane number of gasoline. A Pt/SAPO-11 catalyst has suitable acid sites and metal active sites, and has an excellent catalytic activity for hydrocarbon hydroisomerization. The pore opening of the microporous channels in a SAPO-11 molecular sieve has an elliptical 10-membered ring structure of 0.39×0.63 nm, and it is often used as a carrier for a hydrocarbon isomerization catalyst. In hydrocarbon isomerization reactions, when the conventional large-grain Pt/SAPO-11 prepared from large-grain SAPO-11 is used as a catalyst, the main product is a monobranched isomer; and the monobranched isomer has a low octane number, limiting the use of Pt/SAPO-11 catalyst in the improvement of the octane number of gasoline.
The inventor realizes that it is necessary to add an additional templating agent in the prior-art preparation of the SAPO-11 carrier for the hydrocarbon isomerization catalyst, wherein most of the template agents are organic ones, of which the use will have some impact on the environment and increase the cost of preparation. Therefore, there is an urgent need in the field to develop a method for preparing a SAPO-11 molecular sieve without a templating agent. In addition, it is still a problem to be solved by those skilled in the art to reduce the selectivity to monobranched isomers and increase the selectivity to dibranched isomers of the hydrocarbon hydroisomerization catalyst.